Buffer as hal (#5724)

* Add `as_hal` for `Buffer`

* fmt & CHANGELOG.md update

* Update CHANGELOG.md

* fixed callback name

* allow nested buffer as_hal callbacks

CHANGELOG.md

@@ -78,6 +78,8 @@ By @stefnotch in [#5410](https://github.com/gfx-rs/wgpu/pull/5410)
 
 #### General
 
+- Added `as_hal` for `Buffer` to access wgpu created buffers form wgpu-hal. By @JasondeWolff in [#5724](https://github.com/gfx-rs/wgpu/pull/5724)
+
 #### Naga
 
 - Implement `WGSL`'s `unpack4xI8`,`unpack4xU8`,`pack4xI8` and `pack4xU8`. By @VlaDexa in [#5424](https://github.com/gfx-rs/wgpu/pull/5424)

wgpu-core/src/resource.rs

@@ -932,6 +932,28 @@ impl<A: HalApi> Texture<A> {
 }
 
 impl Global {
+    /// # Safety
+    ///
+    /// - The raw buffer handle must not be manually destroyed
+    pub unsafe fn buffer_as_hal<A: HalApi, F: FnOnce(Option<&A::Buffer>) -> R, R>(
+        &self,
+        id: BufferId,
+        hal_buffer_callback: F,
+    ) -> R {
+        profiling::scope!("Buffer::as_hal");
+
+        let hub = A::hub(self);
+        let buffer_opt = { hub.buffers.try_get(id).ok().flatten() };
+        let buffer = buffer_opt.as_ref().unwrap();
+
+        let hal_buffer = {
+            let snatch_guard = buffer.device.snatchable_lock.read();
+            buffer.raw(&snatch_guard)
+        };
+
+        hal_buffer_callback(hal_buffer)
+    }
+
     /// # Safety
     ///
     /// - The raw texture handle must not be manually destroyed

wgpu/src/backend/wgpu_core.rs

@@ -98,6 +98,14 @@ impl ContextWgpuCore {
         }
     }
 
+    pub unsafe fn buffer_as_hal<A: wgc::hal_api::HalApi, F: FnOnce(Option<&A::Buffer>) -> R, R>(
+        &self,
+        id: wgc::id::BufferId,
+        hal_buffer_callback: F,
+    ) -> R {
+        unsafe { self.0.buffer_as_hal::<A, F, R>(id, hal_buffer_callback) }
+    }
+
     pub unsafe fn create_device_from_hal<A: wgc::hal_api::HalApi>(
         &self,
         adapter: &wgc::id::AdapterId,

wgpu/src/lib.rs

@@ -3547,6 +3547,30 @@ impl Buffer {
         }
     }
 
+    /// Returns the inner hal Buffer using a callback. The hal buffer will be `None` if the
+    /// backend type argument does not match with this wgpu Buffer
+    ///
+    /// # Safety
+    ///
+    /// - The raw handle obtained from the hal Buffer must not be manually destroyed
+    #[cfg(wgpu_core)]
+    pub unsafe fn as_hal<A: wgc::hal_api::HalApi, F: FnOnce(Option<&A::Buffer>) -> R, R>(
+        &self,
+        hal_buffer_callback: F,
+    ) -> R {
+        let id = self.id;
+
+        if let Some(ctx) = self
+            .context
+            .as_any()
+            .downcast_ref::<crate::backend::ContextWgpuCore>()
+        {
+            unsafe { ctx.buffer_as_hal::<A, F, R>(id.into(), hal_buffer_callback) }
+        } else {
+            hal_buffer_callback(None)
+        }
+    }
+
     /// Use only a portion of this Buffer for a given operation. Choosing a range with no end
     /// will use the rest of the buffer. Using a totally unbounded range will use the entire buffer.
     pub fn slice<S: RangeBounds<BufferAddress>>(&self, bounds: S) -> BufferSlice<'_> {